This invention relates to the field of differential mechanisms and, more particularly, to differential mechanisms of the type in which the casing enclosing the differential pinions and gears is rotated by the drive shaft of a powered vehicle.
It previously has been suggested that the casing for such a differential mechanism might be fabricated from opposed half-casings of identical shape and configuration. Such a casing has been utilized in a self-propelled rider vehicle, such as a power lawn mower, wherein wheel driving shafts extend from opposite sides of the differential and a chain driven sprocket is secured to the casing. The half-casings are held together in their assembled position by means of bolts extending through holes in flanges and bosses on each of the half-casings, the bolts having nuts threaded onto the ends thereof. Such a structure appears in U.S. Pat. No. 3,365,984 issued to O. Musgrave on Jan. 30, 1968.
All enclosed rotating differential casings must include suitable bearings between the axle housing and the differential casings and also interiorly of the casings for the differential gears and differential pinions. If the differential casing is to rotate, it must also have means for securing to the casing the ring gear or "crown wheel" to which power is applied by the vehicle drive shaft. In one prior art differential, the casing has oppositely extending journals carried in roller bearings which rotatably support the casing in the axle housing. The casing carries a ring gear which is engaged by a drive pinion for rotating the casing. Typically, the casing is cast in one piece with an access hole for inserting the pinion gears and the side or differential gears after which the access hole can be covered by a plate secured with bolts. Such a differential is disclosed in U.S. Pat. No. 3,896,684 issued to M. J. Duer on July 29, 1975.
One object of the present invention is to reduce the effort required to assemble the interior components in the one piece casing described above. Thus, with the present invention, the differential pinions can be positioned in one half-casing with the differential pinions and their mounting pin before the other half-casing is assembled therewith. This method of assembly results in a savings of time and money over the prior art one piece casing in which the pinions and gears were inserted one at a time and held in place while the half-axles were inserted through the journals and into the gears.
Another object of the present invention is to reduce the components and the time required to assemble the casing. The above-described prior art casing fabricated from opposed half-casings requires a plurality of fasteners to hold it together. The present invention eliminates these fasteners by utilizing the trunnion bearings and the ring gear to hold the half-casings together. The present invention also eliminates the cover and associated fasteners of the above-described one piece casing.